Just got back from IBX still got my stoke on!:D. Just checked out a local area for possible buggying. The problem is rolling Adobe hills upwards of 100' high. I can buggy around them but wind shadow is going to be a big problem. So back to my question, what are the advantages and disadvantages of extending lines? I'm considering another 10 to 15 meters of line. I read through the post about lines and will probably go with what winds of change suggests for type. Thanks for any suggestions. And thanks to all the folks who put IBX ON again.

Hiya Anthony - maybe this thread on extreme kites will help? Sand-Yeti kites up and down dunes and uses 40m lines. Says it took a lot of practice/trial and error to work it all out...

https://www.extremekites.com.au/topic/5822-50-m-blurr-over-t...

"...So back to my question, what are the advantages and disadvantages of extending lines? I'm considering another 10 to 15 meters of line...."

Longer lines allow you to work a larger wind window so you can get longer strokes when seining the kite etc.
Longer lines give you more room for error in turning large kites. Between altitude and low winds I used to always put any FB over 8m on 30m lines.
Disadvantage of the long lines is slower response out of the kite due to the distance the "message" has to travel.

When you say you want to increase 10 -15 m are you talking of going from 10m to 20m or 30m to 40m? Line length increases are anecdotally decreasing exponential in effect [big difference between 10m and 20 m, less difference between 20m and 30m]

Cerebite, that is mostly the answer I was looking for. The steering delay had not occurred to me. The scenario I'm picturing is rolling on my buggy down a Adobe hill and getting behind a 20' to 30' hill. I would need to keep my kite out of the shadow. 25m is somewhat standard I think. So I was thinking 30 to 35 but trying 30 first and seeing how it works out.:P Imagine a hilly pile of gray shale mud.

Agreed, the terrain changes [as I expect the kite skiers can attest] can add an extra dimension to the "gusty" nature of the wind being experienced by the rider and the kite.
Bear in mind that an object will affect the wind for about six times its height downwind but if your obstructions are as closely spaced as you are leading us to believe the wind may actually "ghost" the valleys if you can, as you are proposing, keep the kite "up out of the valleys."